feat: fit the files grid to the width and preview files beside the list on tablets

src/components/email/AttachmentPreviewModal.tsx

@@ -39,6 +39,8 @@ interface Props {
   onShare: () => void;
   /** Save a copy; adds a Download button to the header. */
   onDownload?: () => void;
+  /** Render in place (a split view's side pane) instead of a full-screen modal. */
+  docked?: boolean;
 }
 
 /**
@@ -48,7 +50,7 @@ interface Props {
  * Used by the reader's attachment chips and the Files tab.
  */
 export function AttachmentPreviewModal({
-  item, loading, title, onClose, onOpenExternal, onShare, onDownload,
+  item, loading, title, onClose, onOpenExternal, onShare, onDownload, docked = false,
 }: Props) {
   const c = useColors();
   const styles = React.useMemo(() => makeStyles(c), [c]);
@@ -57,6 +59,9 @@ export function AttachmentPreviewModal({
   // An image the platform can't decode would stay blank; fall back to the
   // external viewer instead. Keyed by URI so the next item starts clean.
   const [failedImageUri, setFailedImageUri] = React.useState<string | null>(null);
+  // The image fits the area it is shown in (a pane, a landscape window),
+  // not a box derived from the window width that ran past the screen.
+  const [imageArea, setImageArea] = React.useState<{ width: number; height: number } | null>(null);
 
   const emlEmail = React.useMemo<Email | null>(() => {
     if (!item?.eml) return null;
@@ -104,13 +109,19 @@ export function AttachmentPreviewModal({
           <ScrollView
             style={styles.flex}
             contentContainerStyle={styles.imageScroll}
+            onLayout={(e) => {
+              const { width: w, height: h } = e.nativeEvent.layout;
+              setImageArea((prev) => (prev && prev.width === w && prev.height === h ? prev : { width: w, height: h }));
+            }}
             maximumZoomScale={4}
             minimumZoomScale={1}
             bouncesZoom
           >
             <Image
               source={{ uri: item.fileUri }}
-              style={{ width: width - spacing.lg * 2, height: width * 1.2 }}
+              style={imageArea
+                ? { width: imageArea.width - spacing.lg * 2, height: imageArea.height - spacing.lg * 2 }
+                : { width: width - spacing.lg * 2, height: width * 1.2 }}
               resizeMode="contain"
               accessibilityLabel={item.name}
               onError={() => setFailedImageUri(item.fileUri ?? null)}
@@ -160,9 +171,8 @@ export function AttachmentPreviewModal({
     }
   };
 
-  return (
-    <Modal supportedOrientations={MODAL_ORIENTATIONS} visible={!!item || loading} animationType="slide" onRequestClose={onClose}>
-      <SafeAreaView style={styles.container} edges={['top', 'bottom']}>
+  const content = (
+      <SafeAreaView style={styles.container} edges={docked ? ['top', 'right'] : ['top', 'bottom', 'left', 'right']}>
         <View style={styles.header}>
           <Pressable
             onPress={onClose}
@@ -210,6 +220,11 @@ export function AttachmentPreviewModal({
         </View>
         {renderBody()}
       </SafeAreaView>
+  );
+  if (docked) return item || loading ? content : null;
+  return (
+    <Modal supportedOrientations={MODAL_ORIENTATIONS} visible={!!item || loading} animationType="slide" onRequestClose={onClose}>
+      {content}
     </Modal>
   );
 }

src/components/files/FilePreviewModal.tsx

@@ -25,6 +25,8 @@ interface Props {
   /** The file to show; null closes the preview. */
   file: PreviewableFileNode | null;
   onClose: () => void;
+  /** Show it in a side pane instead of a full-screen modal. */
+  docked?: boolean;
 }
 
 /**
@@ -35,7 +37,7 @@ interface Props {
  * of fetching it again. The copy is deleted when the preview closes, unless
  * another app got it, in which case the stale-export sweep removes it.
  */
-export function FilePreviewModal({ file, onClose }: Props) {
+export function FilePreviewModal({ file, onClose, docked = false }: Props) {
   const t = useLocaleStore((s) => s.t);
   const [item, setItem] = React.useState<PreviewItem | null>(null);
   const [loading, setLoading] = React.useState(false);
@@ -123,6 +125,7 @@ export function FilePreviewModal({ file, onClose }: Props) {
       item={item}
       loading={loading}
       title={name}
+      docked={docked}
       onClose={onClose}
       onOpenExternal={() => act(
         (local) => shareLocalFile(local, type, name, { keep: true }),

src/lib/__tests__/files-grid.test.ts

@@ -0,0 +1,22 @@
+import { describe, it, expect } from 'vitest';
+import { filesGridLayout } from '../files-grid';
+
+describe('filesGridLayout', () => {
+  it('keeps three columns on a phone', () => {
+    expect(filesGridLayout(411).columns).toBe(3);
+  });
+
+  it('adds columns on a wide window instead of growing the cells', () => {
+    const { columns, cellWidth } = filesGridLayout(1200);
+    expect(columns).toBeGreaterThan(3);
+    expect(cellWidth).toBeLessThan(160);
+    expect(cellWidth).toBeGreaterThanOrEqual(112);
+  });
+
+  it('fits the cells and gaps into the width', () => {
+    for (const width of [360, 411, 800, 1200, 2000]) {
+      const { columns, cellWidth } = filesGridLayout(width);
+      expect(cellWidth * columns + 8 * (columns - 1) + 16).toBeLessThanOrEqual(width);
+    }
+  });
+});

src/lib/files-grid.ts

@@ -0,0 +1,15 @@
+/**
+ * Columns and cell width of the Files grid for a list `width` wide: as many
+ * cells of at least `minCell` as fit, never fewer than three. Cells get a
+ * fixed width, so a short last row keeps the columns of the rows above
+ * instead of stretching its cells across the row.
+ */
+export function filesGridLayout(
+  width: number,
+  { minCell = 112, padding = 8, gap = 8 }: { minCell?: number; padding?: number; gap?: number } = {},
+): { columns: number; cellWidth: number } {
+  const inner = Math.max(0, width - padding * 2);
+  const columns = Math.max(3, Math.floor((inner + gap) / (minCell + gap)));
+  const cellWidth = Math.max(0, Math.floor((inner - gap * (columns - 1)) / columns));
+  return { columns, cellWidth };
+}

src/screens/FilesScreen.tsx

@@ -14,6 +14,7 @@ import {
   TouchableOpacity,
   TouchableWithoutFeedback,
   View,
+  useWindowDimensions,
 } from 'react-native';
 import {
   ChevronLeft, FileText, Folder, FolderPlus, HardDrive, FileImage, FileVideo,
@@ -52,6 +53,8 @@ import { jmapClient } from '../api/jmap-client';
 import { downloadAttachment, shareAttachment } from '../lib/email-export';
 import { secureFetch } from '../lib/client-cert';
 import { getUniqueName } from '../lib/filenode-name';
+import { filesGridLayout } from '../lib/files-grid';
+import { useLayout, useSheetInsets } from '../lib/use-layout';
 import { useBackWhileFocused } from '../lib/use-back-while-focused';
 import { filesBackStep } from '../lib/files-back';
 import type { FileNode } from '../api/types';
@@ -66,7 +69,6 @@ import Dialog from '../components/Dialog';
 import ShareSheet from '../components/files/ShareSheet';
 import { FilePreviewModal, canPreviewInApp } from '../components/files/FilePreviewModal';
 import { MODAL_ORIENTATIONS } from '../lib/modal-orientations';
-import { useSheetInsets } from '../lib/use-layout';
 
 // A file row carries the display name alongside the rest of the node.
 interface FileRow extends FileNode {
@@ -206,6 +208,11 @@ export default function FilesScreen() {
 
   const [viewOverride, setViewOverride] = useState<FilesViewMode | null>(null);
   const viewMode: FilesViewMode = viewOverride ?? defaultViewMode;
+  const { isSplit } = useLayout();
+  // The grid's columns follow its measured width (rotation, tablet panes).
+  const { width: windowWidth } = useWindowDimensions();
+  const [gridWidth, setGridWidth] = React.useState(0);
+  const grid = filesGridLayout(gridWidth || windowWidth);
 
   const uploading = uploadProgress != null;
   const selectionMode = selection.size > 0;
@@ -987,12 +994,14 @@ export default function FilesScreen() {
     body = (
       <FlatList
         data={visibleFiles}
-        key="grid"
-        numColumns={3}
+        // A new column count needs a fresh list.
+        key={`grid-${grid.columns}`}
+        numColumns={grid.columns}
         keyExtractor={(item) => item.id}
         columnWrapperStyle={styles.gridRow}
         contentContainerStyle={styles.gridContent}
-        renderItem={({ item }) => renderGridCell(item)}
+        onLayout={(e) => setGridWidth(Math.round(e.nativeEvent.layout.width))}
+        renderItem={({ item }) => <View style={{ width: grid.cellWidth }}>{renderGridCell(item)}</View>}
         keyboardShouldPersistTaps="handled"
         refreshControl={
           <RefreshControl refreshing={refreshing} onRefresh={onRefresh} tintColor={c.primary} />
@@ -1014,10 +1023,19 @@ export default function FilesScreen() {
     );
   }
 
+  // On a wide window an open file shows beside the list instead of covering it.
+  const previewDocked = isSplit && previewTarget != null;
   return (
-    <View style={styles.container}>
-      {renderHeader()}
-      {body}
+    <View style={[styles.container, previewDocked && styles.splitRow]}>
+      <View style={styles.listColumn}>
+        {renderHeader()}
+        {body}
+      </View>
+      {previewDocked && (
+        <View style={styles.previewPane}>
+          <FilePreviewModal docked file={previewTarget} onClose={() => setPreviewTarget(null)} />
+        </View>
+      )}
 
       <PromptModal
         visible={newFolderOpen}
@@ -1108,7 +1126,7 @@ export default function FilesScreen() {
         onChangeDir={(d) => setSetting('filesDefaultSortDir', d)}
       />
 
-      <FilePreviewModal file={previewTarget} onClose={() => setPreviewTarget(null)} />
+      {!isSplit && <FilePreviewModal file={previewTarget} onClose={() => setPreviewTarget(null)} />}
 
       <ShareSheet
         node={shareTarget}
@@ -1442,6 +1460,9 @@ function makeStyles(c: ThemePalette) {
       flex: 1,
       backgroundColor: c.background,
     },
+    splitRow: { flexDirection: 'row' },
+    listColumn: { flex: 1 },
+    previewPane: { width: '45%', borderLeftWidth: 1, borderLeftColor: c.border },
     header: {
       paddingTop: 60,
       paddingHorizontal: spacing.md,
@@ -1611,7 +1632,6 @@ function makeStyles(c: ThemePalette) {
       gap: spacing.sm,
     },
     gridItem: {
-      flex: 1,
       alignItems: 'center',
       gap: spacing.xs,
       paddingVertical: spacing.md,